Transitional water ecosystems (TWEs), despite their ecological and economic importance, are largely affected by human pressures that could be responsible for significant inputs of litter in the marine environment. Plastic input in coastal ponds, lagoons, river deltas and estuaries, could be driven by a wide range of human activities such as agriculture, waste disposal, municipal and industrial wastewater effluents, aquaculture, fishing and touristic activities and urban impacts. However, it remains unknown what the impact of plastic input in these TWEs could have on natural capital and, therefore, the ability for an ecosystem to provide goods and services to human beings. Given the large interest with regards to the conservation of transitional water ecosystems and the clear exposure risk to plastic and microplastic pollution, this study aims to perform: (i) a bibliometric analyses on existing literature regarding the levels of marine litter in such environments; (ii) a selection among the available literature of homogeneous data; and (iii) statistical analyses to explore data variability. Results suggest that: (i) research on microplastics in these ecosystems did not begin to be published until 2013 for lagoons, 2014 for river mouths and 2019 for coastal ponds. The majority of articles published on studies of microplastics in lagoons did not occur until 2019; (ii) sediments represent the matrix on which sampling and extraction variability allow the statistical analyses on data reported by the literature; (iii) the Analysis of Similarities (ANOSIM) test two-way evidenced that the level of protection of marine and terrestrial areas produced similar values while the habitat type showed low significance in terms of its effect on microplastic levels, shape and size in sediments.

Transitional water ecosystems are targeted by the European Union (EU) Water Framework Directive (WFD, CE 2000/60) monitoring programs in coastal zones. Concerning sediments, activities performed for the WFD focus on a few variables concerning the biochemical composition of organic matter. Our research reports the effects of oxygen availability on the biochemical composition of organic matter in sediments to highlight levels of targeted variables in time and, according to the depth of sediment layer, both under oxygenated and anoxic conditions in a mesocosm study on sediment cores. Results provide evidence that tested factors of interest (i.e., disturbance type, oxygenic versus anoxic conditions; persistence time of disturbance, 0–14 days; penetration through sedimentary layers, 0–10 cm depth) are able to significantly affect the biochemical composition of organic matter in sediments. Large part of the variables considered in this study (total organic carbon (TOC), total phosphorous (TP), total sulphur (TS), Fe, carbohydrates (CHO), total proteins (PRT), biopolymeric carbon (BPC), chlorophyll-a (Chl-a) are significantly affected and correlated to the oxygenation levels and could be good early indicators of important changes of environmental conditions. Monitoring activities performed under WFD guidelines and management strategies of Mediterranean coastal lagoon ecosystems shall include the biochemical composition of organic matter in sediment to provide an exhaustive picture of such dynamic ecosystems.

Cigarette butts (CBs) are among the dominant constituents of marine and beach litter. Few studies have been conducted, and the environmental effects of CBs on marine species are still poorly understood. This study aims to evaluate the ecotoxicological effects on marine organisms of both classic and electronic CBs. Three representative species of different trophic levels in marine ecosystems (Aliivibrio fischeri, bacteria; Phaeodactylum tricornutum, algae, primary producers; Paracentrotus lividus, echinoderms, consumers) were tested. The effects of natural ageing of CBs due to exposure to atmospheric conditions (natural sunlight vs. simulated rain) and for different times (1 vs. 2 weeks) were evaluated. The results were weighted together to obtain a synthetic hazard level to the environment (Class of Hazard) from Sediqualsoft^®. Classic CBs (CCBs) performed the worst and posed a mild to moderate risk compared to electronic CBs (absent Class of Hazard). Smoked classic CBs posed a higher environmental risk than unsmoked. The highest risk was produced by classic CBs after one week of exposure in dry weather. Echinoderms and the body size reduction in normo-formed (72 h) plutei were shown to be the more sensitive organism and endpoint, respectively. We recommend the use of Sediqualsoft^® software for risk assessment studies of sediments contaminated with contaminants of various types, especially in conjunction with a weight of evidence approach (WOE).

Ports are affected by a high rate of sedimentation that requires frequent dredging of the seabed to restore bathymetric levels. In some cases, the sediments consist of a large amount of leaves of phanerogams (e.g., P. oceanica) that must be treated differently from what is required by the Italian law on sediments (Ministerial Decree No. 173/2016), since soils cannot be treated either as sediment or as waste. About one meter of the sediment cores collected in the Port of Sperlonga consisted of organic waste derived from a different stage of seagrass decomposition. To optimize the management, the decomposed organic detritus was characterized from physical-chemical (content of nutrient and pollutants), ecotoxicological and mechanical (microtensile, microscopic structure) points of view, to define different management solutions for the final disposal. The results of this study describe the characteristics of this type of organic detritus, highly present in Mediterranean coastal ecosystems, and allow a better definition of different possible solutions to valorize this resource instead of disposing it in an organic waste landfill. The search for environmentally friendly options for waste management is of particular interest in terms of the green economy, and the reduction of CO₂ emissions as an indirect effect obtained by improving waste recycling.

Microplastic pollution poses an escalating concern, particularly in coastal lagoons rich in biodiversity. This study delved into the occurrence of microplastics (MPs) in Magallana gigas (formerly Crassostrea gigas) from the Orbetello and Varano coastal lagoons (Italy), also investigating the response of these filter-feeding organisms to various colors (P = pink; B = blue; W = white) of high-density polyethylene (HDPE) MP fragments. Oysters were exposed for 7 days under controlled conditions. Subsequently, the oysters underwent analysis for both MP presence and biochemical markers of oxidative stress. Diverse ingestion rates of HDPE were noted among oysters from the two lagoons, eliciting antioxidant responses and modifying baseline activity. The two-way ANOVA revealed the significant effects of treatment (control; HDPE_B; HDPE_P; HDPE_W), site, and the interaction between treatment and site on all biomarkers. Non-metric multidimensional scaling showed a divergent effect of HDPE color on biomarkers. Further investigation is warranted to elucidate the mechanisms underlying the influence of MP color, dose-dependent effects, and the long-term impacts of exposure. Comprehending these intricacies is imperative for devising effective strategies to mitigate plastic pollution and safeguard marine health.

Each year, a staggering 700,000 tons of synthetic dyes are manufactured globally, leading to the release of dye-laden wastewater into aquatic systems. These synthetic dyes resist biodegradation, endangering human and environmental health. Since traditional wastewater treatments are basically unable to remove dyes, exploring the potential of alternative solutions, such as bioremediation, is crucial to reduce dye contamination in aquatic ecosystems. Ficopomatus enigmaticus (Fauvel 1923), listed as one of the 100 worst invasive species in Europe, is considered an invasive ecosystem engineer capable of causing economic and ecological losses. Despite this negative status, the literature suggests its positive contributions to aquatic ecosystems as habitat former and water bioremediator. However, existing evidence on the potential of F. enigmaticus to improve water quality is fragmented and lacks experimental data from laboratory tests. This study examined the potential of Ficopomatus reefs, both living and dead, to enhance water quality by removing contaminants, focusing on methylene blue (MB), one of the most common synthetic dyes. Bioaccumulation and bioadsorption were identified as key mechanisms for dye removal, supported by ATR-FTIR and microscopic analyses. Ficopomatus efficiently removed up to 80% of MB within 24 h. Bioaccumulation in the soft body accounted for 18% of the total removal, while complex adsorption phenomena involving carbonaceous, microalgal, and organic reef components accounted for 82%. Surprisingly, bioremediated solutions exhibited significant effects in ecotoxicological tests on bacteria, indicating the potential of F. enigmaticus to disrupt bacterial quorum sensing related to biofilm formation, and suggesting a possible antifouling action. This study underscores the intricate interplay between F. enigmaticus, water quality improvement, and potential ecological consequences, stressing the need for further investigation into its multifaceted role in aquatic ecosystems.